Introductory Modern Astronomy Pre-assessment

Q1. Arrange the following objects in the order of their distances from the Earth, which one is in the middle?

(a) The asteroid Ada; (b) The Kuiper Belt Object Sedna; (c) The galaxy M31; (d) The planet Neptune; (e) The quasar 3C273.

Q2. A large dot in a star atlas represents

(a) a big star; (b) a bright star; (c) a nearby galaxy; (d) a large star cluster; (e) an important double star.

Q3. The main reason astronomers prefer large telescopes is that they

(a) collect more light; (b) are easier to track stars; (c) have higher magnifications; (d) can be controlled by computers; (e) can easily offset the effect of atmosphere turbulence.

Q4. Which of the following kinds of EM waves can pass through our atmosphere without significant absorption?

(a) gamma-ray; (b) infrared; (c) microwave; (d) ultraviolet; (e) x-ray.

Credit: Addison Wesley

Atmospheric Window 大氣視窗

Q5. A few dark lines and bright lines are present in the spectrum of a star. Which of the following statements concerning the spectrum of this star is correct?

(a) The bright lines belong to its blackbody spectrum; (b) The bright lines are called emission lines; (c) The dark lines belong to its blackbody spectrum; (d) Doppler effect is responsible for the production of the dark lines; (e) The frequencies of the bright and dark lines depend only the surface temperature of the star.

Q6.

(First statement): Since Jupiter-Sun distance is larger than the Earth-Sun distance, (Second statement): therefore, the angular size of the Sun for an Earth-based observer is larger than that for a Jupiter-based observer.

Size and distance in different scales

Q7.

(First statement): Since the Gregorian calendar demands exactly one leap year in every four consecutive years,

(Second statement): therefore, there are 24 leap years between 2001 and 2101.

Q8.

(First statement): Since the ancient Greek divided the whole celestial sphere into 88 constellations,

(Second statement): therefore, each star can only belong to one constellation.

Q9.

(First statement): Since Kepler's first law states that the orbit of a planet around the Sun is elliptical,

(Second statement): therefore, the magnitude of the gravitational force of a planet due to the Sun is greatest when their mutual distance is the smallest.

Kepler’s laws of planetary motion• Law of ellipses

– the orbit of a planet about the sun is an ellipse with the sun at one focus

• Law of equal areas– a line joining a planet and the sun

sweeps out equal areas in equal intervals of time

• Law of harmonies– the square of a planet’s sidereal

period around the sun is directly proportional to the cube of the length of its orbit’s semi-major axis, a

a

Q10.

(First statement): Since the visual magnitude is a linear scale in light intensity,

(Second statement): therefore, a magnitude 1.0 star is about 6.3 times brighter than a magnitude 3.0 star.

Q11.

(First statement): Since the first step of solar system formation is the ejection of accretion disk within about 1 billion years,

(Second statement): therefore, the age of our Solar System is about 1 to 2 billion years.

Q12.

(First statement): Since the rotational period of the Moon relative to the Earth is exactly equal to the orbital period of the Moon relative to the Sun,

(Second statement): therefore, the Moon is in synchronous rotation around the Earth.

Q13.

(First statement): Since the axis of rotation of Venus is almost perpendicular to the orbital plane,

(Second statement): therefore, seasons on Venus is very apparent.

Q14.

(First statement): Since methane in the atmosphere of Neptune scatters blue light,

(Second statement): therefore, Neptune is blue in color.

Q15.

(First statement): Since meteoroids are particles in space that may enter the Earth's atmosphere upon the gravitational pull of the Earth,

(Second statement): therefore, meteor showers can sometimes been seen on Earth.